      # Problem with differentiation with respect to theta

5 replies to this topic

### #1 OxygenPopsycle

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Posted 26 March 2022 - 02:05 PM

I'm using the fx-cg50 and doing problems regarding polar graphs. I have my variables in terms of theta but I cannot figure out how to do d(theta) instead of dx when you hit options and clac in the graph mode. I would really appreciate help from some who know how to change it.

### #2 HappyCalc

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Posted 26 March 2022 - 02:20 PM

As far as I would understand:
You are in Graph Mode (Menu -> 5).
You are using r = <term>.
You want to use differential/integration in OPTN -> Calc Menu.
In the casio docs for differential/integration (Go to SHIFT -> 4 Catalog -> <your command> -> QR) it is stated that you can only use "X" as the variable. That cannot be changed.
The Graph editor uses an X/x if you have Y = <term> and (theta) for r = <term>.
The differential uses X/x for calculation.

Edited by HappyCalc, 26 March 2022 - 02:22 PM.

### #3 HappyCalc

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Posted 26 March 2022 - 02:53 PM

If you want to work with complicated problems you may try a CAS system - for example KhiCAS.
https://www-fourier....nstall_en#casio
There you can use
diff(<term>,<var>) for differential,
plot(<term>,<var>) to show a y= graph and
plotpolar(<term>,<var>) to show a r= graph.
For example try this:
r:=sin(2*theta)
rd:=diff(r,theta)
plotpolar(rd,theta)
That would draw cosine wave in polar coordinates. You can change the variables to whatever you want. You can also name them foo, bar, baz...

### #4 OxygenPopsycle

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Posted 26 March 2022 - 03:43 PM

here's the equation I was trying to enter into my calculator:

https://www.desmos.c...ator/0hqtm8mw1u

### #5 OxygenPopsycle

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Posted 26 March 2022 - 03:59 PM

As far as I would understand:
You are in Graph Mode (Menu -> 5).
You are using r = <term>.
You want to use differential/integration in OPTN -> Calc Menu.
In the casio docs for differential/integration (Go to SHIFT -> 4 Catalog -> <your command> -> QR) it is stated that you can only use "X" as the variable. That cannot be changed.
The Graph editor uses an X/x if you have Y = <term> and (theta) for r = <term>.
The differential uses X/x for calculation.

I can't use x when using  r = <term>.  and the graph becomes a straight line if I use Y = <term>

### #6 HappyCalc

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Posted 31 March 2022 - 05:44 AM

I also tried it. It seems that differential and integration are not allowed in the graph. Most times it shows "Syntax Error" but sometimes it draws the graph but not correct. So I would recommend you to use KhiCAS. It's a little bugged though and crashes in too complex things but for most things it works great. Sometimes it's a bit tricky to use since it uses symbolic variables and would rather show your input instead of calculating it.

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